In recent years, a small-sized game machine that can be carried around (portable game machine) has become widespread, and the contents of executable game programs have become more complicated as processing units come to work at higher speed and memory capacities gets larger. Under such a circumstance, a portable game machine having two display screens has emerged, in which game machine one display screen is used for user operation, and the other display screen is used for displaying a game object, etc.
FIG. 1 is a diagram of the external configuration of an example of such a portable game machine having two screens.
The portable game machine includes a first display screen 1, a second display screen 2, an apparatus case 3 carrying the first display screen 1, and an apparatus case 4 carrying the second display screen 2. The apparatus cases 3 and 4 can be folded together so that the first and second display screens 1 and 2 face each other.
The first display screen 1 is used primarily for input operation in executing a game, and the apparatus case 3 having the first display screen 1 is provided with operation buttons 5, a direction key 6, etc.
In such case, a player inputs necessary information or instructions using the first display screen 1 while following the movement of game characters, etc., appearing on the second display screen 2 as the player executes a game.
A recently suggested technique is shown in FIG. 2, where the first display screen 1 and the second display screen 2 are combined consecutively into a pseudo single display screen encircled with four corners A, B, C, and D to enable execution of a game on a larger display screen.    (Japanese Patent No. 2,917,770)
Referring to FIG. 2 depicting the pseudo single display screen encircled with four corners A, B, C, and D, a case where an object OBJ moves across the boundary between the first display screen 1 and the second display screen 2 is considered.
As shown in FIG. 2, a nondisplay area 7A is present between the first and second display screens 1 and 2, which nondisplay area 7A is formed of display frame portion areas 7 and 8 of the apparatus cases 3 and 4 that are adjacent to each other. Between the first and second display screens 1 and 2, therefore, a distance having a physical size d is present.
In such a case, control of object display in move from the first display screen 1 to the second display screen 2 according to a flow shown in FIG. 3 is assumed in consideration of a time for the object to take to move through the distance having the size d.
In FIG. 3, whether the object OBJ displayed in move on the first display screen 1 has reached an end side of the first display screen 1, which end side is adjacent to the second display screen 2 via the nondisplay area 7A, is determined (step S1). In this determination, the reference point of the object OBJ is determined to be, for example, the central position O of the object OBJ, and when the coordinate position of the reference point of the object OBJ on the first display screen 1 indicates a given size of distance to the side of first display screen 1 that is in contact with the nondisplay area 7A, the object OBJ's reaching the end side of the first display screen 1 is determined (Yes at step S1).
Subsequently, a travel speed (V) and a travel angle (θ) of the object OBJ are calculated (step S2).
Then, based on the calculated travel speed (V) and travel angle (θ) of the object OBJ and the distance d between the first and second display screens, timing T is calculated, in which timing T the object OBJ starts to appear on another display screen, i.e., the second display screen 2 (step 3). This timing T is given by the following equation.T=d/cos θ/v where v is the travel speed of the object OBJ.
At the same time, counting of display timing is carried out (step S4). When a display timing count value matches the timing T (Yes at step S5), an object image is generated to display an image of the object OBJ at a corresponding display position on the second display screen 2, which display position is on an extension line along the travel angle from the first display screen 1, and the generated object image is displayed (step S6).